1. Field of the Invention
The invention relates to video data enhancement, and more particularly, to a method for segmented processing of the intensity distribution of image graphic data.
2. Description of the Prior Art
Please refer to FIG. 1 and FIG. 2. FIG. 1 shows a block diagram of an image processing system 10 according to the prior art, and FIG. 2 shows an image graphic 14 processed by the image processing system 10. The image processing system 10 includes a memory 12 for storing programs, the image graphic 14 awaiting processing, and a processing unit 16 for executing the programs stored in the memory 12. The image graphic 14 has a plurality of pixels 18 arranged in matrix form and includes a region 20 having a predefined feature.
Please refer to FIG. 3. FIG. 3 shows an intensity histogram for the image graphic 14. The pixels 18 in the image graphic 14 are each assigned a gray level, and the intensity histogram shown in FIG. 3 graphs the number of pixels 18 in the image graphic 14 that are at each gray level. According to the prior art, image processing involves using the intensity histogram to select a maximum gray level and a minimum gray level and then performing an image processing operation on the pixels having gray levels falling between the maximum gray level and the minimum g ray level.
Please refer to FIG. 4 and FIG. 5. FIG. 4 shows a transform function for pixels in the image graphic 14, where the horizontal axis represents the original gray level of the pixels before transformation and the vertical axis represents the gray level of the pixel after being transformed by the transform function. From FIG. 4 it can be seen that the transformation process involves first selecting a pixel 14 having a gray level being between the maximum gray level and the minimum gray level, and then using a linear transformation function to convert the original gray level for the pixel to an adjusted gray level being from 0 to 255. FIG. 5 shows an intensity histogram of the image graphic 14 after being processed with the transformation function shown in FIG. 4. From FIG. 5 it can be seen that the pixels having original gray levels between the maximum gray level and the minimum gray level have now been distributed between gray level 0 and gray level 255. The intensity histogram of the image graphic 14 after being processed is therefore more evenly dispersed when compared with the original intensity histogram shown in FIG. 3.
The goal of image processing is to enhance the predefined feature of the region 20 in the image graphic 14 and to increase the difference between the region 20 and the image background. The image processing technique explained above operates on and adjusts the parameters of the graphic image 14 as a whole. For this reason, the image processing technique according to the prior art is only capable of enhancing a primary block in the image graphic and is therefore not able to effectively increase the difference between the region 20 having the predefined feature and the image background. This remains as a problem to be solved.